Graphene is a monolayer of carbon atoms packed into a two-dimensional honeycomb lattice. Graphene exhibits exotic electronic properties originating from its linear band structure dispersion near the Dirac point and the extremely high charge-carrier mobility of both electrons and holes. Thermal decomposition of commercial silicon carbide (SiC) wafers can be used to produce high-quality single-crystalline epitaxial graphene (EG), enabling wafer-size graphene samples to be fabricated for device applications.
Precise control of the dopant carrier type and dopant concentration is important for the development of graphene-based nanoelectronic devices. Conventional doping methods such as ion implantation, which bombard a material with energetic dopant ions and then anneal the doped material, generally damage or destroy the graphene lattice and produce large numbers of defects, which degrade device performance.
Electron and/or hole transport in graphene-based field effect devices can be controlled by an externally applied bias voltage. Recently, effective surface transfer p-type (hole) doping of EG has been demonstrated by modifying the EG surface with a molecular species having strong electron withdrawing properties, such as tetrafluoro-tetracyanoquinodimethane (F4-CNQ). Alternatively, ultrathin metallic films with high electron affinity, such as bismuth, antimony, or gold, can be used to generate p-doped graphene.